1. Technical Field
The present invention relates to a disk apparatus such as a hard disk drive and a head position control method for controlling the position of the head unit that writes data to the disk and/or reads data from the disk. In particular, the present invention relates to a disk drive apparatus and a head position control method that control the position of the head unit on the basis of the spindle current supplied to the spindle motor that rotates the disk.
2. Description of the Related Art
A disk apparatus includes: a disk, which is a data recording medium; a spindle motor for rotating the above described disk; disk rotation speed controlling means for supplying a spindle current to the above described spindle motor to rotate the above described disk at a constant speed; a head unit for accessing the above described disk; an actuator for moving the above described head unit; head position controlling means for driving the above described actuator and controlling the position of the above described head unit; and position detection data generating means for generating position detection data for the above described head unit from servo information that the above described head unit reads from the above described disk, and the disk apparatus reads, by means of the head unit, servo information written to the disk beforehand, generates position detection data for the head unit from this servo information by means of position detection data generating means, drives the actuator and controls the position of the head unit by means of the head position controlling means on the basis of this position detection data, and accesses a target cylinder (track) on the disk by means of the head unit.
In addition to a mode for controlling the position of the head unit on the basis of the above described position detection data (called xe2x80x9cactive modexe2x80x9d in the following descriptions), the above described disk apparatus and especially a small disk apparatus has power-save modes for reducing power consumption. There are a plurality of power-save modes that differ according to whether or not the head unit is retracted from above the disk, whether or not disk rotation is halted, and so forth. Among these power-save modes, one for which the time until return to the active mode is short is a power-save mode in which the power supply of the position detection data generating means is turned OFF while leaving the head unit positioned above the rotating disk. This power-save mode is called xe2x80x9cinitial power-save modexe2x80x9d in the following descriptions.
FIG. 7 shows structural drawings of the interior of the enclosure of disk apparatuses. Here, A is an old type, and B is a new type in which the enclosure has been made smaller. In FIG. 7, reference numeral 1 denotes the disk, reference numeral 2 denotes the spindle motor, reference numeral 3 denotes the head unit, reference numeral 4 denotes the actuator, configured by a voice coil motor (VCM) 41, and a head arm 42 at the tip of which the head unit 3 is mounted, reference numeral 5 denotes a ramp that supports the head arm 42 when the head unit 3 is retracted (unloaded) (more precisely, the head arm 42 moves up a first inclined face of the ramp 5, moves down a second inclined face consecutive to this first inclined face, and is supported by a supporting surface consecutive to this second inclined face), reference numerals 10A and 10B denote the enclosure, reference numeral 11 denotes an inner crash stop that controls the rotation range in an anticlockwise direction (toward the center of the disk) of the head arm 42, and reference numerals 12A and 12B denote a flexible printed cable (FPC) that connects the VCM 41 and the head unit 3 to a control board (not shown) on which the position detection data generating means and head position controlling means are installed. FIG. 7 is a structural drawing showing the head unit 3 unloaded; in the above described active mode and initial power-save mode, the head arm 42 rotates anticlockwise and is detached from the ramp 5, and the head unit 3 is loaded into the air above the rotating disk 1.
In the above described initial power-save mode, position detection data is no longer generated, and therefore the position of the head unit 3 must be controlled, and the head unit 3 positioned at the prescribed position on the disk 1, by a head position controlling means that does not use position detection data. If the head position is not controlled in the initial power-save mode, the head arm 42 may move toward the outer edge of the disk and remain lodged against the first inclined face without being supported by the ramp 5, or move toward the center of the disk and remain lodged against the inner crash stop 11, and in the worst case, the head unit 3 may touch the disk 1 and crash.
In the conventional disk apparatus of FIG. 7A, using the fact that the bias force received by the actuator 4 from the FPC 12A varies according to variations in the position of the head unit 3, in the active mode a VCM current is found beforehand that generates torque that balances the above described bias force at the target position, and in the initial power-save mode, the head unit 3 is positioned at the above described target position by supplying the above described VCM current to the VCM 41.
However, in reducing the size of the disk enclosure and implementing higher density inside the disk enclosure, as in the change from the disk enclosure 10A in FIG. 7A to the disk enclosure 10B in FIG. 7B, in order to achieve further reduction in the size of a disk apparatus, the routing of the FPC is unavoidably changed from the kind illustrated by the FPC 12A in FIG. 7A to the kind illustrated by the FPC 12B in FIG. 7B, and due to this change in the FPC routing, the variation in the bias force from the FPC with respect to the head position is decreased, making it difficult to balance the above described bias force and the torque produced by the VCM, and to fix the head unit at a prescribed position.
FIG. 8 presents graphs showing the bias force received by the actuator from the FPC (the VCM current that generates torque for balancing this bias force) with respect to the position of the head unit in the disk apparatuses in FIG. 7. Here, A shows the case of the old type of disk apparatus in FIG. 7A, and B shows the case of the new type of disk apparatus in FIG. 7B. The above described bias force (VCM current that generates torque balancing this) is different for the case where the head arm 42 is rotated away from the outer edge of the disk and toward the center of the disk, and the case where, conversely, the head arm 42 is rotated away from the center of the disk and toward the outer edge of the-disk (that is to say, there is hysteresis according to the direction of rotation of the head arm 42). In FIG. 8, the characteristic shown by the solid line is for the case of rotation away from the outer edge of the disk and toward the center of the disk, and the characteristic shown by the dotted line is for the case of rotation away from the center of the disk and toward the outer edge of the disk.
As shown in FIG. 8A, in the old type of disk apparatus in FIG. 7A the slope of the characteristic of variation of the bias force from the FPC 12A with respect to the head position is large, and therefore the position of the head unit 3 (the position of the head arm 42) does not differ greatly from the target position even if the VCM current that generates torque balancing the bias force at the target position is somewhat adrift. However, as shown in FIG. 8B, in the new, smaller type of disk apparatus in FIG. 7B, the slope of the characteristic of variation of the bias force from the FPC 12B with respect to the head position is small, and therefore it is difficult to achieve a balance between the bias force and the VCM torque at the target position (the margin for achieving the above described balance is smaller than in the old type). In the area from midway across the disk to the outer edge (the area from 21 to 30 mm from the center of the disk), especially, the above described characteristic slope is small and the margin for preventing the head arm 42 from moving and lodging against the ramp 5 is small.
The present invention solves the above described conventional problems, and has as its object the provision of a disk apparatus and head position control method that enable the head unit to be controlled at a prescribed target position even if head unit position detection data cannot be obtained by means of servo information read from the disk by the head unit, and enable a reduction in size of the disk apparatus to be achieved.
The disk apparatus of the present invention for achieving the above described objective includes: a disk, which is a data recording medium; a spindle motor for rotating the above described disk; disk rotation speed controlling means for supplying a spindle current to the above described spindle motor to rotate the above described disk at a constant speed; a head unit for accessing the above described disk; an actuator for moving the above described head unit; and head position controlling means for driving the above described actuator and controlling the position of the above described head unit, in which the above described head position controlling means obtains the value of the above described spindle current, and, controls the position of the head unit on the basis of the above described spindle current value by using the fact that the above described spindle current varies according to variations in the position of the above described head unit.
Also, the head position control method of the present invention in which a disk apparatus includes: a disk, which is a data recording medium; a spindle motor for rotating the above described disk; disk rotation speed controlling means for supplying a spindle current to the above described spindle motor to rotate the above described disk at a constant speed; a head unit for accessing the above described disk; and an actuator for moving the above described head unit, and controls the position of the above described head unit by using the fact that the value of the above described spindle current varies according to variations in the position of the above described head unit, comprising the steps of:
a. obtaining the value of the spindle current;
b. finding the difference of the above described spindle current value from the target current value; and
c. driving the actuator according to the above described difference.
As described above, according to the present invention, by obtaining the spindle current value, and, by using the fact that the spindle current varies according to variations in the position of the head unit, controlling the position of the head unit on the basis of the above described spindle current value, advantages are provided in that the position of the head unit can be adjusted to a prescribed target position even though head unit position detection data cannot be obtained, and the disk apparatus can be made smaller.